$-\dfrac{5}{3} - \dfrac{4}{5} = {?}$
$ = - {\dfrac{5 \times 5}{3 \times 5}} - {\dfrac{4 \times 3}{5 \times 3}} $ $ = - {\dfrac{25}{15}} - {\dfrac{12}{15}} $ $ = - \dfrac{{25} - {12}}{15} $ $ = -\dfrac{37}{15}$